In a motor control device, when positioning driving is performed in a controlled object having low rigidity, residual vibration sometimes occurs during setting because of machine resonance or the like. In such a case, a feedforward control unit computes, in response to an operation command, a feedforward signal to reduce a signal component of a vibration frequency of the controlled object and uses the feedforward signal for control to perform vibration-damping control for suppressing the residual vibration that occurs in the controlled object. To perform such vibration-damping control, it is necessary to set parameters of feedforward control according to a vibration frequency and an attenuation coefficient of resonance characteristics of a control system including the controlled object.
For example, Patent Literature 1 disclosed a technology including a feedforward signal generator configured to generate, based on a driving command signal, a feedforward signal to minimize a signal component at a vibration frequency of a controlled object and add the feedforward signal to the driving command signal, a resonance-signal computing element configured to receive an input of a signal corresponding to the position, speed, or acceleration of the controlled object and output a resonance signal computed using a transfer function, which has a maximal gain at a vibration-damping frequency, and a resonance estimating element configured to estimate a resonance frequency of the controlled object based on the resonance signal.
However, depending on a controlled object to be driven, residual vibration that occurs during setting of positioning driving sometimes have a waveform in which two or more vibration frequencies are superimposed. In such a case, it is sometimes possible to suppress the residual vibration and perform high-speed positioning driving by applying vibration-damping control to the two or more vibration frequencies. For that purpose, it is necessary to estimate a frequency and an attenuation coefficient from residual vibration in which the two or more frequencies, which are subjected to the vibration-damping control, are superimposed and set the frequency and the attenuation coefficient in the feedforward control unit.
As a problem different from the residual vibration control, there is a method of appropriately setting a notch filter used for suppressing oscillation that make a control system unstable because of a high-frequency machine resonance characteristic. As the method, for example, Patent Literature 2 discloses a technology including a plurality of notch filters configured to attenuate a signal component of a near frequency centering on a notch frequency with respect to an input signal, a plurality of vibration extraction filters in which differ frequency bands are set to be associated with the respective notch filters, the vibration extraction filters extracting vibration components of the set frequency bands from a speed detection signal obtained as a motion amount, and a plurality of notch control units arranged to respectively correspond to the vibration extraction filters and configured to control notch frequencies of the corresponding notch filters to reduce the amplitude of the vibration components extracted by the vibration extraction filters.